Substantially continuous layer of embedded transient protection for printed circuit boards

ABSTRACT

The protection of sensitive components on printed circuit boards by using planar transient protection material in one or more layers of a printed circuit board stackup is disclosed.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Ser. No. 60/653,723, filedFeb. 16, 2005, incorporated herein by reference in its entirety. Thepresent application is related to the application entitled, “SelectiveDeposition of Embedded Transient Protection For Printed Circuit Boards”by Dudnikov et al., which is concurrently filed and the entire contentsof which are hereby incorporated by reference as if fully set forthherein.

BACKGROUND

Printed circuit boards, backplanes, midplanes, printed wiring boards,flex circuits, rigid flex-circuits, multi-chip modules (MCM),interposers and the like are herein referred to collectively as “PCBs”.

A via structure typically provides a conductive path between conductivelayers in the z-axis direction (orthogonal to the x-y plane of a PCB).Via holes are formed by a variety of techniques including but notlimited to laser drilling, mechanical drilling, and techniques based onphoto definition. Via holes are subsequently partially or wholly filledor coated with a conductive material, usually metal. Such via structuresmay be blind, buried, through-hole and may or may not include pads onthe conductive layers, as is well known to those skilled in the art ofPCB design.

Sensitive components on a printed circuit board can be damaged bytransient occurrences of electrostatic discharges (ESD). An ESD ischaracterized by a rapid rise in the order of tens of kilovolts in a fewpicoseconds, for example. Other transient phenomena with lower peakvoltage levels and slower rise-times can also cause damage to theprinted circuit board. For example, a sudden rise in voltage can becaused by a poorly grounded soldering iron, or a power switching relay,or a lightning strike on telecommunication lines that are connected tothe printed circuit board. The term “transient” as used hereinencompasses not only ESD events but any phenomena, of short duration,that directly or indirectly induces voltages and currents into a printedcircuit board and where the amplitudes of such voltages and currents arehigh enough to cause degradation or failure of the electronic componentson the printed circuit board.

FIG. 1A is a schematic that illustrates a printed circuit board 102protected by conductive guard rings 104. Printed circuit board (PCB) 102has a length L and a width W. In FIG. 1A, conductive guard rings 104(only one of which is visible in FIG. 1) are added to the periphery ofeach outer layer of PCB 102 and one or more discrete transientprotection devices can be attached to PCB 102. The guard rings 104 areattached to the chassis ground at the location where I/O connectors 106are mounted to PCB 102. Typically, when a person picks up a PCB, theperson will initially touch the periphery of the PCB. By positioningguard rings 104 along the periphery of PCB 102, guard rings 104re-direct undesired transient currents to chassis ground. Thus,detrimental currents are not allowed to flow to transient sensitivecomponents on PCB 102. However, guard rings fail to protect interiorsurfaces 112 of PCB 102. Another form of transient protection is the useof discrete transient protection devices.

Discrete transient protection devices such as discrete transientprotection devices 108 can be attached to PCB 102 at the location wheresignal and/or power lines enter PCB 102, such as connector 106. However,discrete transient protection devices consume valuable real estate onthe PCB. For example, U.S. Pat. No. 6,657,532 discloses discreteover-voltage protection components made of a thin layer of neatdielectric polymer or glass positioned between a ground plane and anelectric conductor. U.S. Pat. No. 6,657,532 also discloses discreteover-voltage protection components having multi-layers of variablevoltage material. Another non-limiting example of a discrete transientprotection device is a resettablepolymeric-positive-temperature-coefficient (PPTC) device or a voltageswitchable dielectric material (VSDM). Like fuses, PPTC devices helpprotect circuitry from overcurrent damage. However, discrete PPTCdevices consume valuable real estate on the PCB.

Other forms of transient protection include on-chip transient protectiondevices 110, such as zener diodes, for example. However, such on-chiptransient protection devices do not have sufficient capacity toeffectively dissipate large transient events. Both discrete and on-chiptransient protection devices often have excessive amounts of intrinsiccapacitance that makes such devices unsuitable for use in high speedapplications. The primary protection mechanism of both discrete andon-chip transient protection devices is through the conversion ofundesired transient energy into heat. Thus, large transient magnitudesand/or repeated exposure to large transient magnitudes are likely toresult in over-heating that in turn results in performance degradationof such devices.

FIG. 1B is a cross section 150 of the PCB 102 of FIG. 1A taken at 1B.Cross section 150 shows that the PCB comprises multi-layers 160 ofmaterial. Cross section 150 also shows guard ring 104, on-chip transientprotection device 110, connector 106 and discrete protection devices108.

According to certain embodiments of the invention, a voltage switchabledielectric material can be used as transient protection material. In thepast, voltage switchable dielectric material was used to make aninsulating substrate that can be made conductive. When conductive, thevoltage switchable dielectric material is amenable to electrochemicalprocessing such as electroplating for making conductive traces. Such amethod is disclosed by U.S. Pat. No. 6,797,145. Thus, U.S. Pat. No.6,797,145 discloses the use of voltage switchable dielectric material asan insulating substrate that can be made conductive for makingconductive traces.

Thus, in view of the foregoing, an effective form of transientprotection is needed.

SUMMARY OF EXEMPLARY EMBODIMENTS

In certain exemplary embodiments, a printed circuit board (PCB) withintegrated transient protection comprises multiple layers including atleast one reference plane, as defined herein, that includes embeddedplanar transient protection material.

One advantage of using such a reference plane is that the referenceplane acts a heat sink and thus ameliorates degradation of sensitiveelectronic components on the PCB.

These and other embodiments and other features disclosed herein willbecome apparent to those of skill in the art upon a reading of thefollowing descriptions and a study of the several figures of thedrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic that illustrates a printed circuit boardprotected by a conductive guard ring.

FIG. 1B is a cross section of the PCB 102 of FIG. 1A taken at 1B.

FIG. 2 is a schematic that illustrates a polymer region between twocontact regions of a circuit that requires protection from transients.

FIG. 3 is a graph that illustrates voltage clamping provided by embeddedtransient protection material.

FIG. 4A is a schematic that illustrates the protection of a circuittrace from transients by using an embedded transient protection materialto contact a portion of the circuit trace.

FIG. 4B is a graph that illustrates the unsafe voltage levels of regionsthat are not protected by an embedded transient protection material andclamped voltage levels for regions that are protected by an embeddedtransient protection material.

FIG. 5 is a block diagram that illustrates a layer of conductivematerial coated with a layer of transient protection material.

FIG. 6 is a block diagram that illustrates a layer of cured dielectricmaterial bonded with a layer of transient protection material coatedconductive foil.

FIG. 7 is a block diagram that illustrates a layer of dielectricmaterial bonded with a layer of transient protection material coatedconductive foil on one side and a layer of conductive material on theopposing side.

FIG. 8 is a block diagram that illustrates a double-sided compositelayer with a layer of cured dielectric material sandwiched between twolayers of conductive material coated with transient protection materialbonded.

FIG. 9 is a block diagram that illustrates a conductive layer coatedwith a layer of transient protection material and that is bonded to anopposing layer of conductive material coated with a layer of transientprotection material.

FIG. 10 is a block diagram that illustrates a layer of cured dielectricmaterial coated with a layer of transient protection material.

FIG. 11 is a block diagram that illustrates a layer of transientprotection material coated on either side of a cured dielectricmaterial.

FIG. 12A is a block diagram that illustrates a transient protectionregion across a via anti-pad with a via pad.

FIG. 12B is a circuit representation of FIG. 12A.

FIG. 13 is a block diagram that illustrates a transient protectionregion.

FIG. 14A is a block diagram that illustrates a transient protectionregion across a via anti-pad without a via pad.

FIG. 14B is a circuit representation of FIG. 14A.

DETAILED DESCRIPTION

According to certain embodiments, transient protection can be institutedby positioning planar polymer layers into a PCB stackup. Such embeddedplanar polymer materials are herein referred to as transient protectionmaterials. Such transient protection materials may be in the form oflayers that can be laminated to other layers of material in the PCBstackup. Such transient protection materials may incorporate a baseresin of polyimide, epoxy, silicon rubber or other polymers.Alternatively, the transient protection materials can be coated on oneof more layers of the PCB stackup or on one or more layers of conductivematerial as described in greater detail herein.

According to certain embodiments, the layer of transient protectionmaterial can be coated on a layer of conductive foil, eithercontinuously by roll to roll process or by a discrete piece process. Thetransient protection material is then cured using heat processes orother curing processes. In certain embodiments, the transient protectionmaterial is further coated with a resin layer. Non-limiting examples ofresin layers include polyimide, epoxy, silicon rubber or other polymers.

The coated conductive foil is used to make a sandwich by using anotherpiece of coated or uncoated conductive foil on the opposite side of oneor more pieces of uncured dielectric material. The materials of thissandwich are bonded together under heat and pressure to form a corelayer structure. Such a core layer structure can then be processed usingstandard PCB processes to make the features represented in FIG. 12Athrough FIG. 14B, described herein, by methods well known to thoseskilled in the art. The dielectric material can include epoxy,polyimide, teflon or any other polymer. The dielectric material can beun-reinforced as in a film or reinforced with fiberglass of variouscompositions, or reinforced with random fibers of various compositions.Other methods, as are known to those skilled in the art, can be used toform such a core layer structure.

According to another embodiment, the transient protection material thatis coated on the conductive foil can be a polymer such as epoxy orpolyimide. This conductive foil can be bonded to another coated oruncoated conductive foil to form the core layer structure. Such a corelayer structure can be processed using standard PCB processes to makethe features represented in FIG. 12A through 14B, as described herein,by methods well known to those skilled in the art.

According to a further embodiment, the transient protection material canbe selectively removed, by mechanical processes, from areas of the corelayer structure after patterning and etching the conductive foil, wherethe transient protection material is not required. By way ofnon-limiting examples, such processes include laser ablation orsandblasting.

In certain embodiments, in a core layer structure, the combinedthicknesses of the dielectric material and the transient protectionmaterial is less then approximately 4 mils. According to certainembodiments, the dielectric layer thickness is in the range of about 0.1mils to 4 mils. If the conductive foil on one side of the dielectricmaterial and transient protection material composite is a ground planeand the conductive foil on the opposing side of the composite is a powerplane, then the core layer structure has the added benefit of embeddeddistributed capacitance as well as transient protection. A furtherbenefit is the reduction in plane inductance by bringing the powerconductive layer closer to the ground conductive layer. In other words,as the dielectric layer and transient protection material becomesthinner, capacitance is increased and inductance is decreased. Byincreasing capacitance and decreasing inductance quieter powerdistribution systems are produced, which in turn allow cleaner signalsat higher frequencies. Some components, such as discrete capacitors, mayfurther be removed from the surface of the PCB, thus reducing cost.

The amount of capacitance generated in this embedded planar capacitor isdependent upon the dielectric constants of the transient protectionmaterial and the dielectric used in the composite, the planar area ofthe power-ground conductive layer pair and the thickness of thecomposite. The amount of capacitance generated by this structure can becalculated as:

$C = \frac{0.2244ɛ_{r}A}{d}$

where

-   -   C=capacitance in picofarads    -   A=area in square inches    -   ∈_(r)=relative dielectric constant    -   d=dielectric thickness in inches

It should be noted that the ranges of conductive material thicknesses,resin and transient protection material types and the presence ofreinforcement or non reinforcement in the dielectric material asillustrated herein also apply to embedded distributed capacitors withtransient protection.

FIG. 2 is a schematic that illustrates a polymer region (transientprotection region) between two contact regions A and C of a circuitwhere protection from transients is needed. In FIG. 2, symbol Bindicates a region of embedded planar transient protection material. InFIG. 2, region A and region C schematically represent the two contactregions where the transient protection polymer is attached to thecircuit that needs protection from over currents and/or over-voltages.Regions A, B and C are volumetric regions within a given PCB stackuprather than discrete points.

According to certain embodiments, in a majority of cases, the planartransient protection material behaves in a bi-directional manner in thatthe material has the capability of clamping both positive and negativetransients. FIG. 3 is a graph that illustrates voltage clamping providedby planar transient protection material. The resistance of the planartransient protection material that offers bi-directional protectionchanges in response to applied voltage in the manner as indicated inFIG. 3.

In FIG. 3, resistance is represented by the slope of curve 302. A steepslope corresponds to a high resistance. Likewise, a shallow slopecorresponds to a low resistance. During normal operation, the voltageexperienced by the transient protection region is low and thecorresponding resistance is high. However, when the transient protectionregion encounters a high transient voltage event, the resistance of thetransient protection polymer material decreases and consequently allowsmore current to flow through the transient protection region. Thedecrease in resistance in the transient protection region limits thepeak excursion of the transient voltage by clamping the transientvoltage to a safe level while simultaneously re-directing the currentsassociated with the transient voltage to a nearby low impedancereference planar region. As known to those skilled in the art, the lowimpedance reference planar region may be a power distribution plane, achassis ground plane, an analog ground plane, or a digital ground plane.Such a low impedance reference region that is integrated with transientprotection material is herein referred to as a reference plane. Morespecifically, such a reference plane excludes signal planes.

By way of non-limiting examples, the area of the planar transientprotection region is greater than the area containing conductive traces,and is positioned under a reference plane.

When the planar transient protection material is distributed across thePCB, many protection points can be simultaneously incorporated into thePCB. FIG. 4A is a schematic that illustrates the protection of a circuitfrom transients by using an embedded planar transient protectionmaterial to contact a portion of the circuit. FIG. 4A shows PCB region400, victim circuit 404, victim circuit reference 406, and embeddedprotection region 408. For purposes of explanation, assume that atransient voltage 402 enters PCB region 400 at victim circuit 404. Thetransient protection region 408 is incorporated in the middle of theinterconnect. When transient protection region 408 encounters thetransient voltage 402, transient protection region 408 operates to clampthe peak voltage to a safe level. Any excessively high levels of currentdue to transient voltage 402 are shunted to the victim circuit referencewhich can be a power a plane or ground plane, etc. In other words, theexcess current is re-directed to a reference plane.

FIG. 4B is a graph that illustrates the unsafe voltage levels of regionsthat are not protected by an embedded transient protection material andclamped voltage levels for regions that are protected by an embeddedtransient protection material. FIG. 4B shows a graph with voltage alongthe vertical axis 409 a and current on the horizontal axis 409 b. When atransient voltage, such as transient voltage 402 of FIG. 4A, enters thePCB, voltage levels are at unsafe levels 410. However, when thetransient voltage encounters the transient protection region such astransient protection region 408 of FIG. 4A, the voltage is clamped to asafe level 412.

The use of transient protection material in PCBs involves two majoraspects. First, the transient protection material needs to be optimallypositioned within the PCB stackup. Second, the conductive trace and viageometries used for connecting the polymer-loaded core laminates to thecircuits must be added.

According to certain embodiments, the planar transient protectionmaterial can be layered with different materials to form laminates andcores (composites) that are useful for making PCB stackups. FIG. 5through FIG. 11 illustrate various structures that include at least onelayer of planar transient protection material.

The manufacturing techniques for the structures illustrated in FIG. 5through FIG. 11 include single and sequential laminate buildupmanufacturing techniques. However, the techniques may vary fromimplementation to implementation. For example, the transient protectionmaterial can be roller coated on, screen-printed on, lip coated, slotcoated, curtain coated, painted, or sprayed on to a layer of conductivematerial or dielectric material. The layer of conductive material may beprocessed either in roll to roll form as a continuous layer or indiscrete pieces. Further, a layer of conductive material can be coatedwith transient protection material then bonded to other structures bypressing the coated conductive layer to the dielectric material andapplying heat and pressure. A non-limiting example of a dielectricmaterial is a B-Stage material.

FIG. 5 is a block diagram that illustrates a layer of conductivematerial coated with a layer of transient protection material. FIG. 5shows a copper foil 502 coated with a liquid precursor of transientprotection material 504. The liquid precursor, once coated, is thencured. In certain embodiments, the curing process may be performed whenthe structure illustrated by FIG. 5 is further bonded to a substrate asdescribed previously. According to certain embodiments, the transientprotection material can be a non-linear polymer based on resettablepolymeric-positive-temperature-coefficient (PPTC) technology or avoltage switchable dielectric material (VSDM). In certain embodiments,the PPTC polymers have relatively low inherent capacitances in order tooffer transient protection to circuitry with high speed signal lines.The layer of transient protection material 504 can be added on to thelayer of conductive material or copper foil through a variety oftechniques as previously described above.

FIG. 6 is a block diagram that illustrates a single-sided compositelayer comprising a layer of conductive material coated with a layer oftransient protection material bonded to a layer of cured or uncureddielectric material. The structure of FIG. 6 can be made by coating alayer of conductive material 602, such as copper foil, with a layer oftransient protection material 604 on one surface. The resultingstructure is then laminated to a layer of dielectric material 606 byapplying heat and pressure.

FIG. 7 is a block diagram that illustrates a double-sided compositelayer with one layer of transient protection material. The structure ofFIG. 7 is made with a layer of conductive material 702, such as copperfoil, coated with a layer of transient protection material 704. Theresulting structure is laminated on one surface of a layer of dielectricmaterial 706 composed of one or more cured or uncured layers ofdielectric material. Another layer of uncoated conductive material 708is laminated on the other surface of the dielectric material. The aboveoperations for making the structure of FIG. 7 are performedsimultaneously, according to certain embodiments.

FIG. 8 is a block diagram that illustrates a double-sided compositelayer with a layer of cured dielectric material sandwiched between twolayers of conductive material coated with transient protection materialbonded. The structure in FIG. 8 is made by sandwiching a layer ofdielectric material 810 between a layer of conductive material 802, suchas copper foil, coated with a layer of transient protection material 804and another layer of conductive material 806 coated with a layer oftransient protection material 808. The transient protection materials onthe different coated conductive foils may be of different properties.The dielectric material can be composed of one or more cured or uncuredlayers of dielectric material. Heat and pressure is applied to theresulting sandwich. The above operations for making the structure ofFIG. 8 are performed simultaneously, according to certain embodiments.

FIG. 9 is a block diagram that illustrates a layer of conductivematerial coated with a layer of transient protection material and thatis bonded to another layer of conductive material coated with a layer oftransient protection material. The structure of FIG. 9 is made bybonding two structures 502 and 504 of FIG. 5 together. In other wordsthe structure comprises a layer of conductive material 902 coated with alayer of transient protection material 904, which is then bonded with alayer of conductive material 906 coated with a layer of transientprotection material 908. The above operations for making the structureof FIG. 9 are performed simultaneously, according to certainembodiments.

FIG. 10 is a block diagram that illustrates a layer of cured dielectricmaterial to which is added a layer of transient protection material.FIG. 10 shows a layer of dielectric material 1002 and a layer oftransient protection material 1004. The layer of transient protectionmaterial can be added on to a layer of dielectric material through avariety of techniques as previously described above. From thisstructure, other structures may be made if layers of conductive materialare bonded to the surfaces of the layer of dielectric material. Theresulting structures would resemble the structures illustrated in FIG. 6and FIG. 7.

FIG. 11 is a block diagram that illustrates a layer of dielectricmaterial coated with a layer of transient protection material on eitherside. The structure of FIG. 11 is similar to the structure illustratedin FIG. 10 except that the dielectric material 1102 is coated on bothsurfaces (top and bottom) with transient protection material 1104 and1106. Each layer of transient protection material can be added on to thelayer of dielectric material through a variety of techniques aspreviously described above. From this structure, other structures may bemade if layers of conductive material is bonded to the opposing sides ofthe coated layers of dielectric material. The resulting structure wouldresemble the structure illustrated in FIG. 9.

FIG. 12A is a block diagram that illustrates a transient protectionregion across a via anti-pad with a via pad. FIG. 12A shows a crosssection of a transient protection region 1202 that bridges anti-padregions 1204 of a via structure 1206 (or via barrel) with a via pad 1208present. FIG. 12A also shows dielectric region 1210 and contact regionsA and C where the transient protection material contacts the via pad1208 and conductive material 1212, respectively. Such a structure can beused to provide transient protection for a variety of circuit topologieswhere the conducting portion of the circuit to be protected is routedbetween layers of the PCB stackup. The via pads and correspondingantipads may be polygonal shapes including by way of non limitingexample square, round or oval shapes. Any via structure that isconstructed in this manner will be protected by the transient protectionregion, as a via structure that penetrates through the PCB will contactthe transient protection region.

FIG. 12B is a circuit representation of FIG. 12A showing thecorresponding positions of via pad 1208 with conductive regions 1212 andthe transient protection material 1202 connecting the via pad 1208 withthe conductive region 1212.

FIG. 13 is a block diagram that illustrates a transient protectionregion. In particular, FIG. 13 shows a cross section of a transientprotection region comprising a layer of transient protection polymer1302 laminated across two sections, A and C, of two conductive layers1304 and 1308 over an adjacent dielectric layer 1306. The structure ofFIG. 13 can provide transient protection for a variety of circuit toreference plane topologies where two conducting regions are adjacent toeach other and separated by a non-conductive region. Examples includebut are not limited to transmission line structures that are embedded ina reference planar layer and reference planes of different voltagepotentials adjacent to each other. Other non-limiting examples includeslot lines, coplanar waveguides, edge-coupled differential pairtransmission lines and moats of non-conductive areas separatingdifferent ground and power regions in reference planes.

FIG. 14A is a block diagram that illustrates a transient protectionregion across a via anti-pad without a via pad. FIG. 14A shows a crosssection of a transient protection region 1402 that bridges an anti-padregion 1404 of a via structure 1406 that is without a via pad. FIG. 14Aalso shows dielectric region 1408 and contact regions A and C where thetransient protection material contacts the via structure 1406 andconductive material 1412, respectively. Such a structure can be used toprovide transient protection for circuits where non-functional pads arenot present. The antipads may be polygonal shapes including by way ofnon limiting examples: square, round or oval shapes. As prior mentioned,any via structure that is constructed in this manner will be protectedby the transient protection region, as a via structure that penetratesthrough the PCB will contact the transient protection region, evenwithout a via pad present.

FIG. 14B is a circuit representation of FIG. 14A showing thecorresponding positions of via structure 1406 with conductive regions1412 and the transient protection material 1402 connecting the viastructure 1406 with the conductive region 1412.

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

1. A printed circuit board with integrated transient protection, theprinted circuit board comprising: a plurality of stacked layersincluding at least one reference plane, wherein said at least onereference plane includes a layer of conductive material coated with alayer of transient protection material, wherein said layer transientprotection material bridges a region between a part of the layer ofconductive material and a section of a conductive via barrel, whereinsaid part of the layer of conductive material and said section of saidconductive via barrel are co-planar.
 2. The printed circuit board withintegrated transient protection as recited in claim 1, wherein saidtransient protection material comprises resettable non-linear polymershaving properties that protect against at least one of over-current andover-voltage.
 3. The printed circuit board with integrated transientprotection as recited in claim 1, wherein said transient protectionmaterial behaves in a bi-directional manner for clamping both positiveand negative transients of voltage.
 4. The printed circuit board withintegrated transient protection of claim 1, wherein the layer oftransient protection material is parallel with the layer of conductivematerial.
 5. The printed circuit board with integrated transientprotection of claim 1, wherein the layer of transient protectionmaterial is on a different plane to the layer of conductive material. 6.The printed circuit board with integrated transient protection of claim1, wherein the conductive via barrel extends across a plurality of thestacked layers to another conductive layer.
 7. The printed circuit boardwith integrated transient protection of claim 1, wherein the at leastone reference plane further includes a dielectric layer coupled to thelayer of transient protection material, the dielectric layer coupled toa first side of the layer of transient protection material while thelayer of conductive material is coupled to an opposite second side ofthe layer of transient protection material.
 8. The printed circuit boardwith integrated transient protection of claim 7, wherein the at leastone reference plane further includes a second layer of conductivematerial coupled to the dielectric layer, the second layer of conductivematerial coupled to a first side of the dielectric layer while the layerof transient protection material is coupled to an opposite second sideof the dielectric layer.
 9. The printed circuit board with integratedtransient protection of claim 7, wherein the at least one referenceplane further includes a second layer of transient protection materialcoupled to the dielectric layer, the layer of transient protectionmaterial coupled to a first side of the dielectric layer while thesecond layer of transient protection material is coupled to an oppositesecond side of the dielectric layer.
 10. The printed circuit board withintegrated transient protection of claim 8, wherein the layer ofconductive material is a ground plane and the second layer of conductivematerial is a power plane.
 11. A printed circuit board with integratedtransient protection, the printed circuit board comprising: a pluralityof stacked layers including at least one reference plane, wherein saidat least one reference plane includes a layer of conductive materialcoated with a layer of transient protection material, wherein saidtransient protection material bridges a nonconductive region between apart of the layer of conductive material and at least one via pad,wherein said part of the layer of conductive material and said via padare co-planar.
 12. The printed circuit board with integrated transientprotection as recited in claim 11 wherein said nonconductive regioncomprises any one of a square, circle, oblong and polygon.
 13. A printedcircuit board with integrated transient protection, the printed circuitboard comprising: a plurality of stacked layers including at least onereference plane, wherein said at least one reference plane includes alayer of conductive material, the layer of conductive material is coatedwith a layer of transient protection material, the layer of transientprotection material is bonded to at least one surface of at least onelayer of dielectric material.
 14. The printed circuit board withintegrated transient protection as recited in claim 13, wherein athickness of said at least one layer of dielectric material is in therange of 0.3 mils to 80 mils.
 15. The printed circuit board withintegrated transient protection as recited in claim 13, wherein athickness of said at least one layer of dielectric material is in therange of 0.1 mils to 4 mils.
 16. The printed circuit board withintegrated transient protection as recited in claim 13, wherein athickness of the layer of conductive material is in the range of 0.1mils to 10 mils.
 17. A circuit board structure with integrated transientprotection, the circuit board structure comprising: multiple stackedlayers including at least one sub-composite structure, wherein saidsub-composite structure includes at least one layer of transientprotection material and at least two layers of conductive material, andwherein the sub-composite structure has a capacitance of at least 100picofarads per square inch.
 18. The planar distributed capacitancestructure as recited in claim 17, further comprising at least one layerof dielectric material with a thickness in the range of 0.1 mils to 4mils.
 19. A printed circuit board with integrated transient protection,the printed circuit board comprising: a plurality of stacked layersincluding a conductive layer, and an area of transient protectionmaterial disposed in a plane parallel to and in contact with theconductive layer, wherein the area of transient protection materialbridges a gap in the conductive layer, the area of transient protectionmaterial is formed by a coating on the layer of conductive material, thearea of transient protection material is bonded to at least one surfaceof at least one layer of dielectric material.
 20. The printed circuitboard of claim 19, wherein the conductive layer forms at least part of areference plane.
 21. The printed circuit board of claim 19, wherein thegap in the conductive layer is bounded in part by a conductive viabarrel.
 22. The printed circuit board of claim 19, wherein the gap inthe conductive layer is bounded in part by a via pad.
 23. The printedcircuit board of claim 22, wherein the gap in the conductive layer isshaped as any one of: a square, circle, oblong and polygon.
 24. Theprinted circuit board of claim 19, wherein a thickness of said at leastone layer of dielectric material is in the range of 0.3 mils to 80 mils.25. The printed circuit board of claim 19, wherein a thickness of saidat least one layer of dielectric material is in the range of 0.1 mils to4 mils.
 26. The printed circuit board of claim 19, wherein a thicknessof the layer of conductive material is in the range of 0.1 mils to 10mils.
 27. The printed circuit board of claim 19, wherein said transientprotection material comprises resettable non-linear polymers havingproperties that protect against at least one of over-current andover-voltage.
 28. A printed circuit board core, comprising: a firstconductive layer; a transient protection layer coupled to the firstconductive layer; and a dielectric layer coupled to the transientprotection layer, wherein the first conductive layer and the dielectriclayer are on opposite sides of the transient protection layer.
 29. Theprinted circuit board core of claim 28, further comprising: anelectrically conductive via extending through the first conductive layerto the transient protection layer but electrically isolated from thefirst conductive layer.
 30. The printed circuit board core of claim 28,further comprising: a second conductive layer coupled to the dielectriclayer, wherein the second conductive layer and the transient protectionlayer are on opposite sides of the dielectric layer.
 31. The printedcircuit board core of claim 28, further comprising: a second dielectriclayer coupled to the transient protection layer, wherein the dielectriclayer and the second dielectric layer are on opposite sides of thetransient protection layer.